Sinus Infection Causes, Risk Factors, Symptoms, Diagnosis

Sinus infections usually follow a respiratory tract infection, in particular the common cold.

Sinus infection symptoms can include a feeling of pressure or fullness in the face, which is the result inflammation and infection inside sinus cavities.

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A sinus infection occurs when the mucous membranes lining your sinuses (air-filled cavities in your face and head) become infected, usually with a virus but also sometimes bacteria or fungi.

This infection typically follows some kind of nasal blockage, which causes the mucus (produced by the mucous membranes) to build up and become a breeding ground for microorganisms. (1)

"Sinusitis" is a term often used interchangeably with "sinus infection," though the former generally refers to an inflammation of the sinuses, with or without an infection present.

Symptoms of sinus infections are often similar to the common cold or allergies, but there are some notable differences (in particular widespread sinus pressure and pain) that can help in diagnosing the illness. (2)

Causes and Triggers of Sinus Infections

Sinus infections usually follow a viral respiratory tract infection, especially the common cold. A sinus infection caused by a virus is also called viral sinusitis. (3)

A small percentage of people with viral sinusitis also test positive for adenovirus, which is responsible for a range of respiratory illnesses, as well as diarrhea, gastrointestinal inflammation, and neurologic diseases. (4,7)

These viruses can cause increased mucus production, decreased ability for cilia (hairlike cells) to move mucus, and inflammation that restricts the sinus and nasal passages, which together promote the development of a sinus infection.

What Is a Secondary Sinus Infection or Bacterial Sinus Infection?

Viral sinusitis lasts 7 to 10 days. (3)

But if the sinuses remain blocked, a secondary sinus infection could develop.

Rather than being caused by a virus, this secondary sinus infection arises due to bacteria that normally live in the respiratory tract. (8)

Prevotella,Porphyromonas, Fusobacterium, and Peptostreptococcus are the genera that include the most common types of bacteria present in people with chronic sinus infections, or those that last 12 weeks or more. (4)

What Are Fungal Sinus Infections and How Do They Occur?

Fungal sinus infections are a rare type of sinusitis caused by fungi.

Fungal spores or mold are often present in the sinuses, and we breathe these spores in and out all the time. The sinuses, which consist of moist, dark cavities, are the perfect home for fungi, which don't require sunlight for food.

Fungal sinus infections are more common in people with a weakened immune system (such as from diseases like HIV or AIDS or immunosuppressant drugs), uncontrolled diabetes, and prolonged use of antibiotics. (4)

Fungal sinusitis can either be noninvasive or invasive, with the latter class spreading beyond the sinuses to also infect such areas as bone and blood vessels. Invasive fungal sinusitis may be chronic. (14)

Aspergillus fumigatus is the most common fungus associated with fungal sinusitis. It is responsible for both acute fungal sinusitis in people with healthy immune systems and chronic invasive fungal sinusitis in people with immunocompromised systems (usually).

Other Aspergillus species, including Aspergillus flavus and Aspergillus niger, can also cause acute sinusitis in healthy immune systems. These acute forms of sinusitis usually result from a "fungal ball" (mycetoma).

Some people experience a type of fungal infection called allergic fungal sinusitis, which experts believe is an allergic reaction to fungi in the air. (15)

Children have several other risk factors for sinus infections, including day care, pacifier use, bottle use while laying down, and secondhand smoke exposure. (1)

Signs and Symptoms of Sinus Infections

The hallmark symptoms of acute sinus infections are nasal congestion and blockage, a nasal discharge that is thick with a yellow to green coloration, decreased sense of smell, and a feeling of pain, pressure, or fullness in the face.

Other symptoms may include:

Headache

Fever greater than 100.4 degrees F (note that infants under 3 months of age who have a fever should be taken to a doctor as soon as possible)

It may be difficult to tell if a child, especially one of infant or toddler age, has a sinus infection or a simple cold or allergies. Signs of sinus infections in children include irritability, breathing through the mouth, difficulty feeding, and nasally speech. (18)

It's recommended that you see a doctor if your symptoms last more than 10 days, as it may mean you have a bacterial sinus infection, which should be treated with antibiotics.

You should also see a doctor if your symptoms are severe or continue to worsen (such as having a fever greater than 102 degrees F), you have multiple infections within a year, or you experience additional symptoms, such as confusion, vision problems, and stiff neck. (3)

Sinus Infection Testing and Diagnosis

Your doctor will determine if you or your child has a sinus infection based on symptoms (what they are and how long they have lasted) and a physical exam.

Your doctor will look into the nose for signs of nasal polyps, tap the sinus to pinpoint possible infection, and shine a light against the sinus to find signs of inflammation.

She may also conduct various tests, such as a nasal endoscopy, which involves inspecting the sinuses with fiberoptic tube; imaging studies, such as magnetic resonance imaging (MRI) or computerized tomography (CT) scan; allergy tests; or nasal and sinus cultures. (19,20)

What Is a Lingering or Chronic Sinus Infection?

Acute sinus infections will subside either on their own or with treatment within four weeks.

But lingering sinus infections, more commonly known as chronic sinus infections, stick around for at least 12 weeks, sometimes for longer.

Symptoms are similar to acute sinus infections, though typically less severe. To be diagnosed with a chronic sinus infection, you or your child must have at least two of the following symptoms:

Decreased sense of smell

Facial pain, pressure, or fullness

Postnasal drip

Nasal congestion

Young children often also experience chronic cough and bad breath. Fatigue is also a prominent symptom of chronic sinus infections. (21)

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